The present invention relates to a current sensor for detecting the magnitude of current flowing through a conductor.
A known current sensor uses magnetic detection elements such as Hall elements or magnetoresistance effect elements. The current detection performed by a current sensor that uses Hall elements will now be described.
When current flows through a current path such as a wire, the current forms a magnetic field near the current path. The strength of the magnetic field is proportional to the magnitude of the current. When a Hall element is arranged in the magnetic field formed near the current path, the Hall element generates a Hall voltage that is proportional to the current flowing through the current path. A current sensor that uses the Hall element detects the current flowing through the current path based on the Hall voltage.
However, when the strength of the magnetic field acting on the Hall element is small, the proportional relationship of the magnetic field strength and the Hall voltage becomes difficult to maintain. Further, the strength of the magnetic field generated by the current flowing through the current path is low in the first place. To increase the current detection sensitivity of the current sensor, Japanese Laid-Open Patent Publication No. 2002-303642 describes a magnetic core that concentrates the magnetic flux generated by the current flowing through a current path and amplifies the magnetic flux acting on the Hall element. A prior art current sensor including a magnetic core will now be described with reference to FIG. 13.
The current sensor of FIG. 13 is coupled to a bus bar 110. The bus bar 110 is a conductor for supplying power and connected to, for example, a vehicle battery. The current sensor includes a magnetic core 101, a printed circuit board 103, and a case 104. The magnetic core 101 concentrates the magnetic flux generated by the current flowing through the bus bar 110. A Hall element 102 and electronic components are mounted on the printed circuit board 103. The case 104 accommodates the magnetic core 101 and the printed circuit board 103. The case 104 includes a sleeve 104a through which the bus bar 110 is inserted. The magnetic core 101 is C-shaped and includes a clearance CS (gap). The sleeve 104a is inserted into the middle of the space formed at the inner side of the magnetic core 101 so that the magnetic core 101 surrounds the sleeve 104a and the bus bar 110. The clearance CS (gap) of the magnetic core 101 allows for insertion of the Hall element 102. The printed circuit board 103 is connected to a male terminal connector 105, which is arranged on an outer wall of the case 104. The magnetic core 101 concentrates and amplifies the magnetic flux generated by the current flowing through the bus bar 110. Leakage flux generated in the clearance CS acts on the Hall element 102. The magnetic flux acting on the Hall element 102 is amplified. This allows for the current sensor to detect the magnitude of a small current flowing through the bus bar 110. A detection signal corresponding to the Hall voltage of the Hall element 102 is provided to an in-vehicle device (not shown) via the conductor of the printed circuit board 103 and the male terminal connector 105.